SUMMARY Human cytomegalovirus (CMV) causes a spectrum of diseases in immunocompromised patients and serious birth defects when acquired during pregnancy. Limited therapeutic options have fostered efforts towardsthedevelopmentofeffectivevaccinesandantibodytherapeutics.Centraltotheseendeavorshas been a detailed molecular understanding of how CMV enters cells and overcomes intracellular antiviral mechanismstoreplicateandspread. Although CMV transmission occurs orally, CMV tropism for oral mucosal epithelial, endothelial and Langerhans-type dendritic cells has not been studied. In addition, almost all CMV tropism studies conducted thus far have used viruses that have been passaged in cell culture. Our preliminary findings demonstrate that, in contrast to cell culture-derived viruses, CMV shed in urine enters and replicates in epithelialcellsandLCwithlowerefficienciescomparedtofibroblasts,showingthatCMV,asitisexistsin nature,differsdramaticallyfromvirusesgrowninvitro. TheproposedprojectseekstoaddresstheseimportantdeficienciesthroughthefollowingAims: Aim I ? Determine the tropisms of CMV, as it exists in urine and saliva, for oral epithelial, endothelial,andLangerhans-typedendriticcells. Aim II ? Identify the antibodies that are most effective at restricting CMV entry and spread in oral mucosalcells. AimIII?IdentifytheviralgeneticfactorsgoverningCMVtropismsfororalmucosalcells. ThesestudieswillprovideabetterunderstandingoftheinfectiouspropertiesofCMV,asshedinvivo,for cells directly involved in horizontal transmission, will provide data of critical importance for the design of vaccinesandantibodytherapiestoprotectagainstoralCMVtransmission,andwillrevealnovelcelltype- specifichostrestrictionsandviralcountermeasuresthatcouldbeexploitedforintervention.